Typically, when a client computer system requests content from a server, whether over the Internet or, in some instances, over a local and/or wide area network, the request is intercepted at one or more intermediary devices, each of which may alter the request in some way, according to rules installed on the intermediary device. The intent of these rules, and their embodiment, are commonly known as policies. Policies thus define behaviors of the intermediary devices in connection with the requests.
One common form of intermediary device is a cache: a device that maintains copies of requested information (e.g., web pages and the like) so that multiple requests for the same information can be satisfied at the cache. When requests for information are satisfied at a cache, server devices need not receive the requests, process them, and retransmit the same information over a communication channel that links the client devices and the server devices. In the context of typical web browsing, for example, the server devices can be web servers, the client devices can be web clients (e.g., browsers running on personal computers and the like), the communication channel can be an Internet Protocol (IP) network such as the Internet, and the requested information can be web pages and or objects (e.g., images, videos, etc.).
Not surprisingly, in light of the above, caches are often instantiated with or operated according to policies that affect their behaviors in the context of the requests received at the caches and the sites for which the requests are destined. In particular, caches generally are provided with caching policies. These caching policies are sometimes written according to well-established and published guidelines for how certain content is to be cached (e.g. RFC 2616 promulgated by the Internet Engineering Task Force), but such policies do not always work well in the context of certain web sites. For example, with some web sites, specially defined policies may be required in order to dictate caching behavior that optimizes bandwidth savings. Often this may be due to web site designers not considering good cache efficiencies when designing their sites, but in other cases it may be due to the peculiarities of the content hosted at the site, the manner in which the content is stored at the servers, the physical or logical arrangements of the servers hosting the content of interest, or other factors.
In the past, in order to deal with these problematic (from a cache efficiency point of view) web sites, cache providers would have to develop custom solutions or “fixes” as individual customers (e.g. Internet service providers, enterprise network managers, and the like) reported problems. These custom solutions were often only developed after tedious review of voluminous log files obtained from the cache devices and were then distributed somewhat haphazardly as custom configuration files and the like to the cache providers' individual customers. Such distribution occurred through technical briefs, e-mail transmissions or postings on forums, and it was up to the customers to use and install them or not. This of course required knowledgeable customers and there was no guarantee that installing such a custom configuration file would even cure the problem that was initially observed. Thus, each caching problem was treated as a separate instance, with separate and disparate solutions being developed by researchers and others working in isolation from one another and even when solutions were deployed, there was no means of automated feedback to assess their impact or usefulness.